1. Field of the Invention
The present invention relates to an apparatus and method for controlling a variable valve actuation mechanism which varies operating characteristics of an engine valve.
2. Description of the Related Art
Japanese Unexamined Patent Publication No. 2004-092420 discloses a starting control apparatus in which, a starting property of an internal combustion engine is improved by increasing a valve opening amount of an intake valve when an ignition switch or a starting switch is turned on, in a case where the internal combustion engine is equipped with a variable valve actuation mechanism which varies the valve opening amount of the intake valve.
The same publication also discloses that the valve opening amount of the intake valve is increased when an engine speed exceeds a predetermined speed after cranking is started.
Nevertheless, even if an actuator of the variable valve actuation mechanism is controlled in order to increase the valve opening amount of the intake valve at the time when the ignition switch or the starting switch is turned on, friction is large against working of the variable valve actuation mechanism, and actually the variable valve actuation mechanism could not work because engine rotation is not started yet.
Accordingly in the case where the variable valve actuation mechanism is driven, for example, by a motor, it is necessary that the variable valve actuation mechanism includes a motor and a drive circuit which can withstand the large amount of current because a large amount of current is passed through the motor at the start of the engine starting.
In the case where the valve opening amount of the intake valve is increased after the engine speed exceeds the predetermined speed, sometimes the increase in valve opening amount of the intake valve is delayed for the start of the engine starting to worsen the engine starting property.